I have ignored this booting problem for a long time. It shows two lines when booting Ubuntu. Error: Invalid Environment block. Cannot find command hwmatch. This affected upgrades to grub-common and three other packages. I found a solution in the Ubuntu help forum and followed their instructions. https://askubuntu.com/questions/191852/error-invalid-environment-block-press-any-key-to-continue I didn't want to mess with grub because the boot continues, no-biggie, but when upgrades of certain packages are failing I had to find a better solution. As I understand it, I have to replace a file in /boot/grub called grubenv, create a new one which contains default=0. Restart the computer. No more messages during boot. I then did an apt-get update and upgrade. No problem there too.
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